1. Field of the Invention
The present invention relates to an inspection apparatus of a wiring pattern, an inspection method, a detection apparatus, and a detection method for optically extracting a wiring pattern of an uppermost layer in a multilayered wiring substrate for a semiconductor package, on which a plurality of wiring patterns are stacked, for example, via a polyimide insulating layer having transparency, and picking up an image by high resolution to automatically inspect and detect the pattern.
2. Description of the Related Art
In general, in a wiring pattern formed on a multilayered wiring substrate for a semiconductor package for use in a purpose of making an electronic apparatus smaller or lighter, a copper foil is laminated on a polyimide film via an adhesive and patterned/treated by a subtractive process, a semi-additive process or the like, and a portion having a thickness of 5 to 15 μm, and a highest degree of integration has a width of about 10 μm.
In this pattering process step, there is a fear that severe defects are suddenly produced such as thinning (cracking) of the wiring pattern, breaking of wire, shorting, and thickening (protrusion). Therefore, the presence of these defects has heretofore been judged by an open-/short-circuit inspection or a visual inspection. However, the visual inspection raises the issue that skills are required with the miniaturization of the pattern, and fluctuation or defect oversight is caused in an inspection result by an inspector's physical condition or the like. Then, in recent years, various types of automatic inspection apparatuses have been proposed which automatically inspect the presence of defects using cameras (e.g., Jpn. Pat. Appln. KOKAI Publication No. 10-19531 (Example 1) and Jpn. Pat. No. 2962565 (FIGS. 5, 7)). Moreover, it is possible to visually inspect various types of defects existing in a wiring pattern having a minimum width of 10 μm in the multilayered wiring substrate for the semiconductor package, but there is the problem that much inspection time is required for the visual inspection, and product unit price increases accompanying an increase in personnel costs. Therefore, automatic inspection is required. For example, an imaging resolution of 1 μm has to be realized in order to detect ⅓ or more defects within the width of 10 μm. To solve the problem, an imaging method, an inspection method, further a handling method and the like need to be sought in a broad view of the relationship between the imaging resolution and imaging view field (object work size).
In general, in the automatic inspection apparatus which automatically inspects the presence of defects using cameras, a plurality of wiring patterns on the same work are imaged simultaneously, with a time difference, in divided areas or the like by a plurality of sensor cameras (line CCD device, area CCD device, etc.), and the image is recognized. By this process, defects are detected such as thinning (cracking), breaking of wire, shorting, thickening (protrusion) and the like existing in the wiring pattern. As the recognizing process, a method is general in which CAD data (pattern design information) or satisfactory work (work on which the wiring pattern is correctly formed) is registered as a reference master image in advance, and a portion having a difference is judged as a defect by methods such as a comparison process of this master image with an inspection image (inspection object pattern image), and a characteristic extraction process. At this time, the inspection image is reflected noting the wiring pattern formed on the uppermost layer, and the image is picked up without considering any influence of an inner-layer wiring pattern in most cases.
As examples of a reason for this, an inner-layer wiring pattern does not exist in a product, or the imaging of the uppermost-layer wiring pattern is not influenced by an insulating layer substrate type interposed between the wiring patterns, substrate thickness, substrate color, transmission/reflection spectral sensitivity and the like even in a product in which the inner-layer wiring pattern exists. Even when the inner-layer wiring pattern exists and exerts a slight influence, the influence can be easily eliminated by threshold value adjustment at imaging time, and it is not necessary to regard reflection influence of the inner-layer wiring pattern as an optical problem from the beginning.
However, in a case where the conventional inspection apparatus is used, in the multilayered wiring substrate for the semiconductor package, when the thickness of the polyimide film insulating layer interposed between the wiring patterns and having transparency is about 10 to 25 μm, and small, and attempts to image the uppermost-layer wiring pattern with a high resolution are made, the wiring pattern existing in the inner layer is reflected, and a clear pattern image cannot be obtained noting only the uppermost-layer wiring pattern.
Moreover, optical conditions are important for performing the above-described inspection using the image picked up by the camera. Unless the defect can be optically visualized, secure inspection is impossible even if the process algorithm is sophisticated.
Furthermore, it has also been proposed that fluorescent components generated from the insulating layer be detected using fluorescence illumination on the wiring pattern and insulating layer portion to thereby extract and inspect the wiring pattern portion in a pseudo manner. However, in this method, an image in which a wiring pattern edge is extracted in the pseudo manner is obtained by fluorescence emission. Therefore, defects such as pinholes in the wiring pattern and cracks existing on the top side of the wiring pattern cannot be detected. The wiring pattern needs to be noted and inspected in order to guarantee the quality of the multilayered wiring substrate for the semiconductor package. Therefore, it has been demanded that apparent quality guarantee be more firmly performed as a package inspection in such a manner that a copper wiring pattern can be directly seen, surface defects such as micro pinholes and dents, or quality of filled vias for performing interlayer connection can be observed, and high-speed signal transmission is realized. Moreover, when the inspection noting the wiring pattern can be performed, a manufacturing process is checked by monitoring good/bad points of the wiring pattern formed during the manufacturing, and control of a process state can be involved in order to keep the manufacturing process itself to be optimum.
Moreover, the invention described in Jpn. Pat. Appln. KOKAI Publication No. 10-19531 is an invention in which the wiring pattern is imaged as a dark image to thereby image the wiring pattern. Therefore, in the method described in Jpn. Pat. Appln. KOKAI Publication No. 10-19531, the wiring pattern can only be picked up as the dark image, and it is impossible to realize sophisticated imaging to such an extent that surface defects like the micro pinholes and dents, or filled via quality to perform interlayer connection can also be observed.
Furthermore, in the invention described in Jpn. Pat. No. 2962565, laser light having a specific wavelength (450 nm or less) is radiated, and the wiring pattern is picked up as a bright image utilizing a difference between a reflectance from the wiring pattern and that from a polyimide-based insulating film (ON AL). However, the usual CCD does not have any sensitivity with respect to light having a wavelength of 450 nm or less, and a special imaging system is required. On the other hand, as to the wavelength (e.g., around 550 nm) to which the usual CCD has sensitivity, there is little difference between the reflectance from the wiring pattern and that from the polyimide-based insulating film (ON AL). In the method disclosed in Jpn. Pat. No. 2962565, it is difficult to image only the wiring pattern of the uppermost layer and not to image the wiring pattern of the inner layer.
Moreover, in the automatic inspection of the wiring pattern, it is necessary to image the wiring pattern having a large area in a short time. However, the method disclosed in Jpn. Pat. No. 2962565 is so-called point scanning. In the method, the laser light is condensed to irradiate the wiring pattern, and the laser light with which the wiring pattern is irradiated is scanned to thereby image the wiring pattern. Therefore, much time is required. Further in the method disclosed in Jpn. Pat. No. 2962565, intensity of the laser light reflected in various directions on the wiring pattern is detected, and information such as an arrangement angle of the wiring pattern is obtained based on a detected value. Therefore, at least two detection systems need to be disposed, and the constitution is complicated. Furthermore, since the detected value from each system is calculated to thereby restore a wiring pattern state, the calculation amount is enormous.